Borosilicate glass compositions and uses thereof

ABSTRACT

Glass, glass compositions, methods of preparing the glass compositions, microfluidic devices that include the glass composition, and methods of fabricating microfluidic devices that include the glass composition are disclosed. The borosilicate glass composition includes silicon dioxide (SiO 2 ) in a range from about 60% to 74% by total composition weight; boric oxide (B 2 O 3 ) in a range from about 9% to 25% by total composition weight; aluminum oxide (Al 2 O 3 ) in a range from about 7% to 17% by total composition weight; and at least one alkali oxide in a range from about 2% to 7% by total composition weight. In addition, the borosilicate glass has a coefficient of thermal expansion (CTE) that is in a range between about 30×10 −7 /° C. and 55×10 −7 /° C. Furthermore, the borosilicate glass composition resists devitrification upon sintering without the addition of an inhibitor oxide.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority under 35 U.S.C. § 119 ofEuropean Patent Application Serial No. 02 292 981.4 filed on Dec. 3,2002.

This application is related to U.S. utility patent application entitled“A Microfluidic Device and Manufacture Thereof” filed on 12 May 2004 andaccorded Ser. No. 10/843,949, now issued as U.S. Pat. No. 7,007,709,which is a continuation of Ser. No. 10/454,985, filed 4 Jun. 2003 andnow issued as U.S. Pat. No. 6,769,444, which is a continuation of Ser.No. 10/163,215, filed 4 Jun. 2002 and now issued as U.S. Pat. No.6,595,232, which is entirely incorporated herein by reference.

TECHNICAL FIELD

The present invention is generally related to glass compositions and,more particularly, is related to borosilicate glass compositions anduses thereof.

BACKGROUND OF THE INVENTION

Borosilicate glass is a well-known glass that has a low coefficient ofthermal expansion (CTE) 33×10⁻⁷/° C. and high chemical durability (i.e.,resistance to acidic and alkaline reagents). As a result, borosilicateglass has become an important component in many types of laboratoryequipment that require chemical durability.

However, powdered borosilicate glass (borosilicate glass frit) undergoesdevitrification (i.e., formation of cristobalite, tridymite, and/orquartz crystals that lead to a decrease in glass properties) duringsintering at between about 700-800° C. Crystal formation with high CTElowers the mechanical strength of the sintered glass product. Lowermechanical strength is also due to the volume change associated with thephase transformation from an amorphous state to the crystal state. Thus,when powdered borosilicate glass is used to make frit layers on asubstrate having a low CTE, devitrification increases global CTE of thefrit layer and thereby causes cracks to form.

One potential solution to overcome devitrification in powderedborosilicate glass is to add an inhibitor oxide such as alumina to thepowdered borosilicate glass. The addition of the alumina tends toinhibit the formation of high expansion crystals. The addition ofalumina, however, causes the sintering ability of the frit glass todecrease. In addition, the fluidity of the frit glass is decreasedduring sintering when alumina has been added.

Thus, a heretofore unaddressed need exists in the industry to form aglass frit that addresses the aforementioned deficiencies and/orinadequacies.

SUMMARY OF THE INVENTION

A representative borosilicate glass includes a borosilicate glasscomposition. The borosilicate glass composition includes silicon dioxide(SiO₂) in a range from about 60% to 74% by total composition weight;boric oxide (B₂O₃) in a range from about 9% to 25% by total compositionweight; aluminum oxide (Al₂O₃) in a range from about 7% to 17% by totalcomposition weight; and at least one alkali oxide in a range from about2% to 7% by total composition weight. In addition, the borosilicateglass has a coefficient of thermal expansion (CTE) that is in a rangebetween about 30×10⁻⁷/° C. and 55×10⁻⁷/° C. Furthermore, theborosilicate glass composition resists devitrification upon sinteringwithout the addition of an inhibitor oxide.

A representative method of making a borosilicate glass includes forminga homogeneous mixture by mixing a plurality of components. Thecomponents of the homogeneous mixture include silicon dioxide (SiO₂) ina range from about 60% to 74% by total composition weight, boric oxide(B₂O₃) in a range from about 9% to 25% by total composition weight,aluminum oxide (Al₂O₃) in a range from about 7% to 17% by totalcomposition weight, and at least one alkali oxide in a range from about2% to 7% by total composition weight. Next the method includes meltingthe homogeneous mixture; and sintering the homogeneous mixture forming aborosilicate glass. The borosilicate glass has a coefficient of thermalexpansion (CTE) that is in a range between about 30×10⁻⁷/° C. and55×10⁻⁷/° C. In addition, the homogeneous mixture resistsdevitrification upon sintering without the addition of an inhibitoroxide.

A representative microfluidic device includes a first assembly and asecond assembly. The first assembly includes a microstructure that isdisposed on a first substrate. The second assembly includes a secondsubstrate and a precursor material. The second assembly and the firstassembly are positioned such that the precursor material and themicrostructure are adjacent one another. The second assembly ispositioned on the microstructure after the first assembly is presinteredand adhered thereto by heat treatment to form a one-piece microstructuredefining at least one recess between the first and second assemblies.The precursor material includes silicon dioxide (SiO₂) in a range fromabout 60% to 74% by total composition weight; boric oxide (B₂O₃) in arange from about 9% to 25% by total composition weight; aluminum oxide(Al₂O₃) in a range from about 7% to 17% by total composition weight; andat least one alkali oxide in a range from about 2% to 7% by totalcomposition weight. In addition, the precursor material has acoefficient of thermal expansion (CTE) that is in a range between about30×10⁻⁷/° C. and 55×10⁻⁷/° C. Further, the precursor material resistsdevitrification upon sintering without the addition of an inhibitoroxide.

A representative method of fabricating a microfluidic device includesproviding a first assembly and a second assembly. The first assemblyincludes a microstructure that is disposed on a first substrate. Thesecond assembly includes a second substrate and a precursor material.The precursor material includes a borosilicate glass composition thathas a coefficient of thermal expansion (CTE) that is in a range betweenabout 30×10⁻⁷/° C. and 55×10⁻⁷/° C. In addition, the borosilicate glasscomposition resists devitrification upon sintering without the additionof an inhibitor oxide. The precursor material includes silicon dioxide(SiO₂) in a range from about 60% to 74% by total composition weight;boric oxide (B₂O₃) in a range from about 9% to 25% by total compositionweight; aluminum oxide (Al₂O₃) in a range from about 7% to 17% by totalcomposition weight; and at least one alkali oxide in a range from about2% to 7% by total composition weight. In addition, the precursormaterial has a coefficient of thermal expansion (CTE) that is in a rangebetween about 30×10⁻⁷/° C. and 55×10⁻⁷/° C. Further, the precursormaterial resists devitrification upon sintering without the addition ofan inhibitor oxide. The method also includes disposing the firstassembly on the second assembly such that the precursor material and themicrostructure are adjacent one another and heating the first assemblyand the second assembly to form a one-piece microstructure defining atleast one recess between the first and second assemblies.

Other compositions, systems, methods, devices, features, and advantagesof the present invention will be or become apparent to one with skill inthe art upon examination of the following drawings and detaileddescription. It is intended that all such additional systems, methods,features, and advantages be included within this description, be withinthe scope of the present invention, and be protected by the accompanyingclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the invention can be better understood with reference tothe following drawings. The components in the drawings are notnecessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the present invention. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 is a cross-sectional view that illustrates an exemplarymicrofluidic device that includes the borosilicate glass composition ofthe present invention.

FIGS. 2A′ through 2E illustrate cross-sectional views of an exemplaryfabrication process of the microfluidic device illustrated in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Embodiments of the present invention provide for borosilicate glasscompositions, methods of preparation thereof, and structuresincorporating borosilicate glass formed from the borosilicate glasscompositions. Embodiments of the present invention overcome at leastsome of the aforementioned deficiencies and inadequacies described aboveby providing borosilicate glass compositions that self-inhibit theformation of detrimental crystals. As discussed above, formation of oneor more of these crystals may likely cause an increase in thecoefficient of thermal expansion (CTE). Consequently, the glass productloses mechanical strength due, at least in part, to the volume changeassociated with crystal formation.

In addition, the borosilicate glass compositions may be formulated toresist thermal shock, be chemically resistant to acidic and alkalinechemical reagents, and have low softening points, while not devitrifyingand causing crystals.

In particular, a glass formed from an embodiment of the borosilicateglass composition preferably has a coefficient of thermal expansion(CTE) that is in a range between about 30×10⁻⁷/° C. and 55×10⁻⁷/° C. Inaddition, the borosilicate glass composition preferably resistsdevitrification upon sintering without the addition of an inhibitoroxide (i.e., alumina powder), as discussed above, which decreasessintering ability and fluidity of the borosilicate glass compositionduring sintering.

Embodiments of the borosilicate glass composition include, among others,silicon dioxide (SiO₂), boric oxide (B₂O₃), aluminum oxide (Al₂O₃), andat least one alkali oxide. The alkali oxide may preferably includelithium oxide (Li₂O), potassium oxide (K₂0), and sodium oxide (Na₂O).Not intending to be bound by theory, it appears that Al₂O₃ plays a rolein inhibiting the formation of cristobalite and tridymite crystalsduring the sintering of the borosilicate glass composition. In addition,it appears that B₂O₃ increases the meltability of the borosilicate glasscomposition and acts as an efficient flux without significantlyincreasing the CTE of the borosilicate glass, while the alkali oxideincreases the CTE of the borosilicate glass.

It is also possible to add conventional finishing agents such as As₂O₃or Sb₂O₃, fluorides, bromides, or chlorides, with the provision thattheir total content does not exceed approximately 1%. If desired,bleaching agents may be added. It is also possible to color the glass byadding conventional coloring elements.

In particular, one embodiment of the borosilicate glass compositionincludes SiO₂ in a range between about 60% and 74% by total compositionweight, B₂O₃ in a range between about 9% and 25% by total compositionweight, Al₂O₃ in a range between about 7% and 17% by total compositionweight, and the at least one alkali oxide in a range between about 2%and 7% by total composition weight.

In addition, the borosilicate glass composition may include one or morealkaline-earth oxides. The alkaline-earth oxides include barium oxide(BaO), strontium oxide (SrO), calcium oxide (CaO), and magnesium (MgO).Furthermore, the borosilicate glass composition may include one or morerare-earth oxides such as, but not limited to, lanthanum oxide (La₂O₃),tantalum oxide (Ta₂O₃), yttirium oxide (Y₂0₃), and cerium oxide (CeO₂).The sum of the weight percentages of the alkaline-earth oxides and/orthe rare-earth oxides is in a range between about 0.1% and 7% by totalcomposition weight. Again, not intending to be bound by theory, itappears the alkaline-earth oxide increases the CTE of a borosilicateglass formed from the borosilicate glass composition.

Furthermore, the borosilicate glass composition may also includezirconium oxide (ZrO₂) in the range between about 0.1% and 5% by totalcomposition weight. Not intending to be bound by theory, addition of theZrO₂ to the borosilicate glass composition appears to enhance resistanceto alkaline reagents.

In another embodiment the borosilicate glass composition preferablyincludes SiO₂, B₂O₃, Al₂O₃, Li₂O, and ZrO₂. Not intending to be bound bytheory, it appears that Na₂O and/or K₂O can increase the likelihood ofand extent of devitrification and are therefore not included in thisembodiment. In addition, B₂O₃ is included to increase melt ability,stability, and reduce glass viscosity, and Li₂O increases melt ability,lowers glass viscosity, and also increases CTE. In particular, addingAl₂O₃ to the borosilicate glass composition causes substitution of Si⁴⁺with Al³⁺ in the atomic glass network. Consequently, Li⁺ is stronglybonded to the glass network because of the strong coupling between Li⁺and Al³⁺, which occurs from a need to maintain electroneutrality at thelocal atomic level. The strong bond of Li⁺ to the glass network enhancesthe acidic resistance of the borosilicate glass composition. Addition ofthe ZrO₂ to the borosilicate glass composition appears to enhance alkaliresistance.

This embodiment of the borosilicate glass composition can be used tofrom a glass that has a CTE in a range between about 30×10⁻⁷/° C. and45×10⁻⁷/° C. upon sintering. The borosilicate glass formed from theborosilicate glass composition has a softening point in a range betweenabout 600 and 1000° C. In addition, the borosilicate glass has a percentweight loss of less than about 10 milligrams/dm² according to the DIN12116 acid resistance test (i.e., determining the percent weight lossafter placing the borosilicate glass in a boiling aqueous solution ofhydrochloric acid 6N for 6 hours). Furthermore, the borosilicate glasshas a percent weight loss of less than about 250 milligrams/dm²according to the ISO 695 alkali resistance test (i.e., determining thepercent weight loss after placing the borosilicate glass in a boilingaqueous solution of mixed alkali for 3 hours).

In particular, the borosilicate glass composition includes SiO₂ in therange between about 68% and 73% by total composition weight, B₂O₃ in therange between about 13% and 17% by total composition weight, Al₂O₃ inthe range between about 8% and 15% by total composition weight, Li₂O inthe range between about 2% and 5% by total composition weight, and ZrO₂in the range between about 1% and 3% by total composition weight. Inaddition, the sum of the weight percent of SiO₂, Al₂O₃, and ZrO₂ in theborosilicate glass composition is less than 78% by total compositionweight.

The method of forming borosilicate glass composition includes forming ahomogeneous mixture of the components of the borosilicate glasscomposition described above. The homogeneous mixture is then melted at atemperature of about 1650±10° C. in a platinum-rhodium crucible or thelike, which may take from about 5 to 10 hours. After the homogeneousmixture is melted, the melted composition is quenched into deionizedwater and then milled in dry conditions using an alumina ball mill orthe like into borosilicate frit particles. Then sieved particles aredisposed into a mold (i.e., silicon mold) and sintered at a temperatureabout 20° C. above the softening point of the borosilicate glass (i.e.,about 850° C.) for about 20 to 40 minutes.

Table 1 includes three (Compositions 1-3) representative inventiveborosilicate glass compositions, a previous borosilicate glass chemicalcomposition, and two other glass compositions (Compositions A and B). Inaddition, glass properties (e.g., bulk glass CTE, softening point, DIN12116 acid resistance test, and ISO 695 alkali resistance test) andglass powder properties (e.g., sintered glass CTE and crystalline phase)were measured for each composition listed above and are included inTable 1 for comparative purposes. As can be seen from Table 1,Compositions 1-3 have CTE's (sintered glass) and softening points lessthan the previous borosilicate glass composition. In addition,Compositions 2 and 3 have comparable chemical resistances to that of theprevious borosilicate. Compositions 1-3 do not form cristobalitecrystalline phases, while the previous borosilicate and Compositions Aand B form cristabalite crystalline phases. Thus, Compositions 1-3 havephysical characteristics superior to that of the previous borosilicatechemical composition and Compositions A and B.

TABLE 1 previous Comp. 1 Comp. 2 Comp. 3 borosilicate Comp. A Comp. B (%weight) (% weight) (% weight) (% weight) (% weight) (% weight) SiO₂ 6571 71 81 70 74.7 B₂O₃ 15 15 15 13 15 13 Al₂O₃ 11 10.7 9.7 2 3 9 Li₂O 23.3 3.3 — 1 3.3 Na₂O — — — 4 — — K₂O 2 — — — 6 — BaO 5 — — — 5 — ZrO₂ —— 1 — — — Bulk 39.1 34.6 33.8 32.5 40.1 35.6 Glass CTE (10⁻⁷/ ° C.)Sintered 39.7 35 35.2 79.2 121 80.6 Glass CTE (10⁻⁷/ ° C.) Softening 790808 795 823 — 777 Point (° C.) DIN 42 1.7 2.8 <0.1 — 0.4 12116 (mg/dm²)ISO — 226 153 102 — 113 695 (mg/dm²) Crystalline Amorphous Amorphous/Amorphous/ Cristobalite Cristobalite Cristobalite/ Phases Quartz QuartzQuartz

In another embodiment of the present invention, the borosilicate glasscompositions can be used in microfluidic devices as precursor materialsthat may enhance the contact between components of the microfluidicdevice (i.e., a substrate and a microstructure). The borosilicate glassformed from the borosilicate glass composition has a CTE that iscompatible with the CTE of the other components of the microfluidicdevice upon sintering. The compatible CTEs allow fabrication and usewithout mechanical stresses. In addition, the borosilicate glasscomposition may be formulated so that the borosilicate glass formed fromthe borosilicate glass composition is chemically resistant to chemicalreagents (i.e., acidic and/or alkaline chemical reagents) that may beused during the operation of the microfluidic device.

Reference will now be made to the figures. FIG. 1 is a cross-sectionalview of a representative microfluidic device 10 that incorporates aborosilicate glass composition of the present invention. Themicrofluidic device 10 includes a first substrate 11, a microstructure13, a precursor material 15, and a second substrate 17. Themicrostructure 13 is disposed between the first substrate 11 and theprecursor material 15. The precursor material 15 is disposed on thesecond substrate 17 adjacent the microstructure 13.

The first substrate 11, the microstructure 13, and second substrate 17can be made of materials such as, but not limited to glasses, glassceramics, ceramics, metals, semiconductors, or combinations thereof. Thefirst substrate 11, the microstructure 13, and the second substrate 17can be constructed of the same or of different materials.

The first substrate 11, the microstructure 13, the precursor material15, and the second substrate 17 can be combined to form recesses boundedby the microstructure 13 and the precursor material 15. The recesses canhave various cross-sectional dimensions such as, but not limited to,substantially square, substantially rectangular, substantiallyhexagonal, semicircular, or substantially circular. For example, FIG. 1shows the recesses to be substantially square.

In addition, the total volume of the recesses can vary depending on theparticular application. The degree of perforation (i.e., the empty spacebetween the ridges of the microstructure 13) of the microstructure 13determines the total volume. The preferred embodiment of themicrostructure 13 includes a microstructure that is highly perforated sothat the total volume of the recesses is large. For example, thepercentage of empty space bounded by the microstructure 13 and theprecursor material 15 is typically greater than about 50%. However,lower volume percentages are contemplated and are within the scope ofthe present invention.

In particular, the first substrate 11 and the second substrate 17 have athickness in the range of about 200 μm to about 3 millimeters (mm), andpreferable at least 200 μm. The microstructure 13 can have a width inthe range of about 100 μm to about 300 μm and a height of up toapproximately 800 μm; the widths of the resulting recesses are in therange of about 50 μm to more than about 1000 μm.

As depicted in FIG. 1, the walls of the microstructure 13 that form therecesses can have a constant thickness. However, the thickness of thewall may be constant, tapered, flaring, or a combination thereof and canbe tailored for a particular application.

Embodiments of the microfluidic device 10 can include at least oneporous structure (i.e., first substrate 11, second substrate 17, and/ora microstructure 13). The porous structure may be used to performseparations within the microfluidic device 10. In addition, a porousstructure can be used to affix a catalyst thereto, as discussed below.

In general, the microfluidic device 10 may include appropriate passages(not shown) for inlet and outlet of one or more fluids that flow withinthe microfluidic device 10. The inlet/outlet can be formed through thefirst substrate 11, the second substrate 17, and/or the microstructure13.

The precursor material 15 can be made of the borosilicate glasscompositions described above. The preferred embodiment of the precursormaterial 15 includes SiO₂, B₂O₃, Al₂O₃, Li₂O, and ZrO₂. This compositioncan be used to form a borosilicate glass that has a CTE in a rangebetween about 30×10⁻⁷/° C. and 45×10⁻⁷/° C. upon sintering. In addition,the borosilicate glass formed from the borosilicate glass compositionpreferably has a softening point in a range between about 600 and 1000°C. Further, the borosilicate glass preferably has a percent weight lossof less than 10 milligrams/dm² according to the DIN 12116 acidresistance test as described above. Furthermore, the borosilicate glasspreferably exhibits a percent weight loss of less than 250milligrams/dm² according to the ISO 695 alkali resistance test asdescribed above.

In particular, the precursor material 15 includes a borosilicate glasscomposition having SiO₂ in the range between about 68% and 73% by totalcomposition weight, B₂O₃ in the range between about 13% and 17% by totalcomposition weight, Al₂O₃ in the range between about 8% and 15% by totalcomposition weight, Li₂O in the range between about 2% and 5% by totalcomposition weight, and ZrO₂ in the range between about 1% and 3% bytotal composition weight. In addition, the sum of the weight percent ofSiO2, Al₂O₃, and ZrO₂ in the precursor material 15 is less than about78% by total composition weight.

In another embodiment, the precursor material 15 includes an organicmedium such as, but not limited to, a thermoplastic medium, athermosetting medium, or a photopolymerizable medium. The organic mediumis added to the precursor material 15 to assist in vacuum molding of theprecursor material 15. Subsequently, the organic medium present in theprecursor material 15 is substantially eliminated during pre-sinteringand sintering.

In general, the CTE of the first substrate 11, the microstructure 13,the precursor material 15, and the second substrate 17 are compatible toprevent mechanical stresses in the microfluidic device 10 duringfabrication and use. In addition, the materials of the first substrate11, the microstructure 13, the precursor material 15, and the secondsubstrate 17 can be selected to be chemically resistant to chemicalreagents (i.e., acidic and/or alkaline chemical reagents) that may beused during the operation of the microfluidic device 10.

Within the microfluidic device 10, fluids involved in theexperiment/test may come into contact only with surfaces of themicrofluidic device 10, which are under complete control. In thisregard, the surfaces of the microfluidic device 10 can be modified to beactive or passive. For example, the surface can include a catalyst orthe surface can be covered with a film (e.g., polysiloxane) to make thesurface neutral. In addition, the microfluidic device 10 may includeelectrical conductors, electrodes, and the like, that may be used aheaters, sensors, and the like.

For the purposes of illustration only, and without limitation,embodiments of the present invention will be described with particularreference to the below-described fabrication methods. Note that notevery step in the process is described with reference to the processdescribed in the figures hereinafter. Therefore, the followingfabrication processes is not intended to be an exhaustive list thatincludes every step required to fabricate the embodiments of themicrofluidic devices of the present invention.

FIGS. 2A′ through 2E are cross-sectional views of a representativefabrication of the microfluidic device 10 illustrated in FIG. 1. FIGS.2A′ and 2B′ are cross-sectional views of the formation a first assembly19, while FIGS. 2A″ and 2B″ are cross-sectional views of the formationof a second assembly 21.

FIGS. 2A′ and 2B′ illustrate the formation (e.g., vacuum molding) of themicrostructure 13 on the first substrate 11 to form the first assembly19. FIGS. 2A″ and 2B″ illustrate the formation (e.g., vacuum molding) ofthe precursor material 15 on the second substrate 17 to form the secondassembly 21.

In one embodiment the first assembly 19 and the second assembly 21 canbe pre-sintered at about 500° C. for about 5 hours prior to the stepshown in FIG. 2C. In particular, the pre-sintering process includes:heating the first assembly 19 and/or the second assembly 21 from about20° C. to about 500° C. over the course of about 2 hours, holding thetemperature of the first assembly 19 and/or the second assembly 21 forabout 1 hour, and reducing the temperature from about 500° C. to about20° C. over a 2 hour time period.

FIGS. 2C and 2D illustrate the combination of the first assembly 19 andthe second assembly 21, where the second assembly 21 is disposed on topof the first assembly 19 such that the microstructure 13 is in contactwith the precursor material 15. Thereafter, the first assembly 19 andthe second assembly 21 are sintered at about 820° C. for about 5 hoursto form the microfluidic device 10, as shown in FIG. 2E.

In particular, the sintering process includes: heating the firstassembly 19 and/or the second assembly 21 from about 20° C. to about820° C. over the course of about 2 hours, holding the temperature of thefirst assembly 19 and/or the second assembly 21 for about 20 minutes,reducing the temperature from about 820° C. to about 500° C. over a 10minute time period, and reducing the temperature from about 500° C. toabout 20° C. over a 2 hour time period.

It should be emphasized that the above-described embodiments of thepresent invention, particularly, any “preferred” embodiments, are merelypossible examples of implementations, merely set forth for a clearunderstanding of the principles of the invention. Many variations andmodifications may be made to the above-described embodiment(s) of theinvention without departing substantially from the spirit and principlesof the invention. All such modifications and variations are intended tobe included herein within the scope of this disclosure and the presentinvention and protected by the following claims.

1. A borosilicate glass, wherein the CTE of the borosilicate glass is ina range from about 30×10⁻⁷/° C. to 45×10⁻⁷/° C., wherein the softeningpoint of the borosilicate glass is in a range between about 600 and1000° C., wherein the borosilicate glass has a percent weight loss ofless than 10 milligrams/dm² according to an acid resistance test,wherein the borosilicate glass has a percent weight loss of less than250 milligrams/dm² according to an alkali resistance test, and whereinthe borosilicate glass comprises: SiO₂ in the range from about 68% to73% by total composition weight; B₂O₃ in the range from about 13% to 17%by total composition weight; Al₂O₃ in the range from about 8% to 15% bytotal composition weight; and lithium oxide (Li₂O) in the range fromabout 2% to 5% by total composition weight; wherein the borosilicateglass resists devitrification upon sintering without the addition of aninhibitor oxide, and wherein the borosilicate glass further includes oneor more alkaline-earth oxides or rare-earth oxides, wherein the sum ofthe weight percentages of the one or more alkaline-earth oxides orrare-earth oxides is in a range between about 0.1% and 7% by totalcomposition weight.
 2. A borosilicate glass, wherein the CTE of theborosilicate glass is in a range from about 30×10⁻⁷/° C. to 45×10⁻⁷/°C., wherein the softening point of the borosilicate glass is in a rangebetween about 600 and 1000° C., wherein the borosilicate glass has apercent weight loss of less than 10 milligrams/dm² according to an acidresistance test, wherein the borosilicate glass has a percent weightloss of less than 250 milligrams/dm² according to an alkali resistancetest, and wherein the borosilicate glass comprises: SiO₂ in the rangefrom about 68% to 73% by total composition weight; B₂O₃ in the rangefrom about 13% to 17% by total composition weight; Al₂O₃ in the rangefrom about 8% to 15% by total composition weight; and lithium oxide(Li₂O) in the range from about 2% to 5% by total composition weight;wherein the borosilicate glass resists devitrification upon sinteringwithout the addition of an inhibitor oxide, and wherein the borosilicateglass further includes substantially none of one or more of potassiumoxide (K₂O) or sodium oxide (Na₂O).
 3. The borosilicate glass of claim 1or 2, wherein the borosilicate glass further includes: zirconium oxide(ZrO₂) in the range between about 0.1% and 5% by total compositionweight.
 4. The borosilicate glass of claim 1 or 2, wherein theborosilicate glass further includes: zirconium oxide (ZrO₂) in the rangebetween about 1% and 3% by total composition weight.
 5. The borosilicateglass of claim 1 or 2, wherein alkaline-earth oxide is selected from atleast one of barium oxide (BaO), strontium oxide (SrO), calcium oxide(CaO), and magnesium oxide (MgO), and wherein the rare-earth oxide isselected from at least one of lanthanum oxide (La₂O₃), tantalum oxide(Ta₂O₃), yttrium oxide (Y₂O₃) and cerium oxide (CeO₂).